Musannaf Ibn Abi Shayba 3:3499

Ghundar narrated to us, from Shu'bah, from Qatadah, from Ikrimah, that he said regarding a group of people who are in the countryside (as-sawad) while traveling on the day of Eid al-Fitr or Eid al-Adha: They should gather and pray, and one of them should lead them.